NAVLE Avian and Exotic Animal Medicine 4

Question 1

A 4-year-old African grey parrot presents with progressive ataxia, regurgitation, and marked crop dilation. Radiographs reveal a markedly dilated proventriculus. PCR testing confirms Avian Bornavirus (ABV). Which of the following statements about the pathophysiology of Proventricular Dilatation Disease (PDD) is most accurate?

Accepted Answer

ABV triggers a T-cell mediated lymphoplasmacytic ganglioneuritis targeting the autonomic ganglia of the GI tract

Answer

PDD results from Avian Bornavirus causing lymphoplasmacytic ganglioneuritis — a T-cell mediated inflammatory infiltrate that destroys the autonomic ganglia innervating the gastrointestinal tract. The loss of ganglionic innervation results in failure of peristalsis and progressive dilation of the proventriculus and ventriculus, not direct myocyte destruction. ABV does not cause IgE-mediated hypersensitivity, and replication is not limited to crop epithelium.

Question 2

A free-ranging red-tailed hawk is presented after being found unable to fly. Physical exam reveals bilateral mydriasis unresponsive to light, weakness, and flaccid paralysis of the nictitating membrane. The bird is afebrile and alert. Which toxin is most consistent with this clinical picture, and what is the proposed mechanism?

Accepted Answer

Type C botulinum toxin — cleaves SNAP-25, blocking presynaptic acetylcholine release at the neuromuscular junction

Answer

Limberneck (avian botulism) caused by Clostridium botulinum type C toxin is classic in raptors ingesting maggots or carcasses. The toxin cleaves SNAP-25 (a SNARE complex protein), preventing presynaptic vesicle fusion and blocking acetylcholine release at the neuromuscular junction — producing flaccid paralysis, mydriasis, and weakness of the nictitating membrane. Organophosphates cause miosis (not mydriasis) and cholinergic signs; lead causes CNS signs and GI effects; zinc primarily causes hemolysis.

Question 3

A 6-year-old bearded dragon (Pogona vitticeps) presents with anorexia, lethargy, and swollen limbs. Radiographs show lytic bone lesions and periosteal proliferation. Bloodwork reveals marked heterophilia and a PCV of 18%. Cytology of a fine-needle aspirate from a swollen limb reveals large, round organisms with a clear halo and a basophilic nucleus consistent with yeast. Which diagnosis and treatment is most appropriate?

Accepted Answer

Chrysosporium anamorph of Nannizziopsis vriesii (CANV) infection — itraconazole and surgical debridement

Answer

CANV (Chrysosporium anamorph of Nannizziopsis vriesii) is a primary fungal pathogen of agamid lizards, including bearded dragons, causing deep mycosis with lytic bone lesions, skin ulceration, and systemic dissemination. The large round yeast with a clear halo on cytology is characteristic. Treatment requires long-term itraconazole combined with aggressive surgical debridement of affected tissue. Devriesea agamarum is a bacterial pathogen. Ophidiomyces is a snake fungal disease. Basidiobolus causes GI infections in reptiles but has a different clinical presentation.

Question 4

During a routine health exam on a 3-year-old Burmese python, you palpate a mid-body mass. Ultrasound reveals a well-defined, echogenic structure with posterior acoustic shadowing adjacent to the left kidney. The snake has been fed a rodent diet exclusively and appears otherwise healthy. What is the most likely diagnosis and the most important next diagnostic step?

Accepted Answer

Renal calculus — measure uric acid and perform contrast radiography to assess urinary outflow

Answer

In snakes, a well-defined echogenic structure with posterior acoustic shadowing adjacent to the kidney is characteristic of a nephrolith (renal calculus). Snakes are uricotelic, and uric acid nephropathy with urolithiasis is the most common renal pathology in captive pythons, often secondary to dehydration, excess protein, or renal disease. The critical next step is measuring uric acid (hyperuricemia suggests active renal impairment) and using contrast radiography or CT to determine if urinary outflow is obstructed. Hepatic lipidosis and hepatocellular carcinoma are not consistent with acoustic shadowing adjacent to the kidney.

Question 5

A 2-year-old intact female sugar glider (Petaurus breviceps) presents with a 1 cm, firm, non-painful mass on the dorsal midline of the head. The owner reports the mass appeared over 2 weeks. On exam, the animal is bright and alert with no neurologic signs. Cytology of a fine-needle aspirate reveals cells with abundant pale cytoplasm, round nuclei, and prominent nucleoli in a proteinaceous background. What is the most likely diagnosis?

Accepted Answer

Scent gland adenocarcinoma arising from the frontofrontal gland

Answer

Male sugar gliders have a prominent frontofrontal (forehead) scent gland, but females can develop neoplasia of the same glandular tissue. Adenocarcinoma of the frontofrontal scent gland presents as a rapidly growing firm mass on the dorsal midline of the head. Cytology typically reveals epithelial cells with abundant pale cytoplasm and prominent nucleoli in a proteinaceous background consistent with glandular secretory tissue gone malignant. Dermatofibrosarcoma and lymphoma are less likely without inflammatory history or systemic signs. An abscess would typically show degenerate neutrophils and bacteria.

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE - North American Veterinary Licensing Examination Practice Test

NAVLE Avian and Exotic Animal Medicine 4